DE 196 23 749 A1 describes the manufacture of randomly distributed micro lenses by means of lithography and etching techniques. The element generates a rotation symmetrical Gauss distribution out of a convergent radiation. However, the form of the lenses and the openings are defined by the process and can only be varied in very few parameters.
U.S. 200210145797 A1 describes the profile formation and homogenization for a projection screen with the purpose of generating a homogeneously filled rectangular radiation.
P. Rhodes, D. Shealy; “Refractive optical systems for irradiance redistribution of collimated radiation: their design and analysis”; Appl. Opt. Vol. 19, No 20, p. 3545; 1980 describes the deformation of a determined radiation profile in a balanced energy distribution.
The invention is based on the task of creating an optical array for radiation profile formation and/or homogenization, by optimizing a specific light distribution in a radiation zone or by minimizing light losses.
The invention approaches the task where the number of edges as well as the lengths of the lenses edge segments of each individual lens of the micro lens combination are defined through a point distribution (P) and each individual lens has on each of these points a Voronoi point (2), which consequently define a Voronoi Region (VR(P)), in which the equation below describes a Voronoi lens (1):
      z    ⁡          (      r      )        =                    c        ·                  r          2                            1        +                              1            -                                          (                                  1                  +                  k                                )                            ·                              c                2                            ·                              r                2                                                          +                  a        4            ·              r        4              +                  a        6            ·              r        6              +    …  
Each Voronoi lens has a minimal radius of curvature R, which has a magnitude 10 to 200 times larger than the maximum distance dmax, which is the maximum of all distances from the lenses edge points to the fixed vertexes of the lenses. Each vertex of the Voronoi lenses has a clearance A to the Voronoi point of each of the Voronoi lenses that lies between 0 and the radius of curvature R of the Voronoi lens. Thereby the position of the vertex can be selected so that it provides the maximum intensity for an optical configuration of the radiation point.
The Voronoi lenses preferably have a diameter from 10 μm to 25,000 μm. Another approach defines the diameter between 1λ and 1000λ, where λ is the work wavelength. The work wavelength is within the range between 100 nm and 10 μm. The lens depth z is within the range of 0.1 μm and 150 μm. The lens depth z is defined by the height difference between the vertex and the edge point of the Voronoi lens, in which the dmax distance is defined. The radius of curvature R lies between 5 μm and 100,000 μm.
The materials used for each wavelength (or wavelength range) may be optically transparent materials such as silicon, quartz, calcium fluoride, glass or polymers.
In general, Quartz or CaF2 are used for the UV range, Glass and Polymers for the visible range and Silicon for the IR range. The thickness of the materials preferably lie between a tenth to one millimeter.
According to the invention, initially, a set of points is fixed over a component surface. Such a set of points mathematically constitute the Voronoi points of the edges of the individual lenses, as well as the number of edges, the geometric shape and the surface size of each of the individual lenses of the micro lens combination. These individual lenses can be subsequently identified as Voronoi lenses.
Furthermore, preferably the position of the Voronoi lenses vertexes is fixed, whereby the points, and thus the lines and/or the surfaces generate the maximum intensity of the optical path of rays in the radiation zone.
The invention is particularly oriented to produce a form of truncated Gauss distribution and different source structures (such as dipoles, quadruple poles, hexapoles) for the Sigma level (aperture simulations). The desired light beam form in the radiation zone will be achieved through the specific Voronoi lenses vertex distribution in the micro lens array, such as for example ring shaped Disars, Quasars or their multiple adjoining dispositions.
Thereby, A is the distance of the Voronoi points in the projection over the components surface, which can either be equal to or larger than zero. Therefore, it must be considered that if a distance A is proportionally large in comparison to the lenses dimension, this will lead to a significant height difference between the adjoining Voronoi lenses, so that the distance A is especially smaller than the selected radius of the Voronoi lenses. The height difference can be minimized by the optimization of the Z distance.
The form of the borders of each Voronoi lens influences the form of the partial light beam that passes through the Voronoi lenses. Therefore, a triple edge shaped Voronoi lens produces a triple edge shaped partial light beam.
A single form of Voronoi lens can be designed through an adequate selection of Voronoi point positions, such as a six-edge configuration.
If in the design of the microstructures, the size of the micro lenses is smaller than the lateral coherent length, a homogenization of light from an infinite distance source takes place through an incoherent overlapping of the partial opening of the entrance field.
For a Gauss shaped intensity distribution, it is advisable to select a Voronoi point distribution, in which the Voronoi lenses are statically arranged in a triple-edge, quadruple edge and sextuple edge shaped array.
The surface of the Voronoi lenses produces a lighted region in the radiation zone of the path of rays with a size corresponding with a partial beam. Therefore the larger Voronoi lenses produce a larger illumination region, and the smaller Voronoi lenses a smaller illumination region. This dimension cannot be varied with the lenses radius of curvature. Large radii produce small fields.
Furthermore, in a particular embodiment of the invention it is foreseen that the surface shape of the Voronoi lenses is an open surface which is no longer described over a radial indication. Such surface shapes are for example spherical or cylindrical shapes.
These shapes can be described with the classic lens equation, whereby a4 is the spherical coefficient and the first imprint of the conical section of the depicted surface, where k is the conical constant:
      z    ⁡          (      r      )        =                    c        ·                  r          2                            1        +                              1            -                                          (                                  1                  +                  k                                )                            ·                              c                2                            ·                              r                2                                                          +                  a        4            ·              r        4              +                  a        6            ·              r        6              +    …  
Where 0≦r≦dmax and c=1/R.
Through the large scale dimensional possibilities of this optics, a beam of rays can be transformed into any of the desired beam shapes. The design may be calculated with the procedure described in Lars Erdmann, Arnaud Deparnay, Falk Wirth and Robert Brunner: “MEMS based lithography for the fabrication of micro optical components” Micromachining Technology for Micro-Optics and Nano-Optics II, edited by Eric G. Johnson, Gregory P. Nordin, Proceedings of SPIE Vol. 5347, p. 79-84, 2004 and the structure will be illuminated. A Digital Mirror Device serves as a mask generator in the lithographic procedure. When compared to the current State of the Art techniques, the described procedure offers more design parameters freedom. The different parameters are:                Radius of curvature (always equal or different)        Spherical/aspherical, concave/convex lenses or their combinations        Changes in the position of the optical center        Polygonal form        Polygon filling        
The structure can be produced with the help of different lens shapes. It is possible to have rectangular, square or arbitrary (Voronoi) picketing. For coherent illumination problems, it is preferable to use statically distributed Voronoi structures. If possible, the entrance beam should completely and convergently illuminate the refractive element. The use of incoherent sources may be preferred. The use of many adequate micro lenses makes the exit shape largely independent from the entrance shape and from entrance beam intensity distribution.